It is well known to electrolyze brine and other halides in electrochemical cells containing anode and cathode compartments separated by either an impervious ion selective membrane or a diaphragm. The power and consequently cost required for electrolysis of halides in these cells is, however, relatively high; one of the reasons being that the cathode reaction is the reduction of water to produce hydrogen gas. This reaction requires voltages of approximately 1.5 to 2.0 volts.
Research and development efforts have been directed at reducing the power levels for the electrolysis of brine by lowering the voltage required through the use of a different cathode reaction. For example, air cathodes (gas depolarized electrodes) that reduce oxygen to hydroxyl ions have been examined. Air cathodes require substantially lower voltages, around 0.5 volt, resulting in significantly reduced power requirements for the electrochemical cell; and although hydrogen gas is not produced in the air cathodes, the hydrogen gas produced by cathodes that electrolyze water is typically not used by industry.
These research and development efforts have not been totally successful. For instance, the cell performance although initially stable can drop dramatically during cell operation. Accordingly, there is a constant search in this art for electrolysis cells having gas depolarized electrodes that yield stable cell performance during operation.